Contrail Gaps and other Questions

There was an interesting post over on the New York SkyWatch blog, which raised many of the common questions that people have about various contrail anomalies. I’ve attempted to answer all of the questions here:

Question #1, why [do] jet contrails appear as if the jet engine is being deliberately turned on and off?
It’s because the jet is flying through uneven areas of temperature and humidity. Explained here

Question #2, Explain why jet aircraft are leaving persistent contrails in grid patterns?
Because some jets fly north-south, and some east-west on airways that are several miles wide, and where they cross you get a grid. Winds at altitude blow at around 90mph, and these blow the trails across the sky, increasing the size of the grid.

Question #3, Shouldn’t the entire sky be filled with contrails? Would we ever see any truly blue sky again if all jets left persistent contrails behind?
Sometimes there are a lot of contrails, and they do spread out and cover the sky. Sometimes there are only a few. Sometimes there are none. It depends on the weather. There are only a certain number of jets flying overhead every day. They have to be at the right altitude for contrails to form. In some weather conditions this is limited to only the highest jets, or sometimes just jets in a narrow band of humid air. On very cold humid days you will see a lot of contrails, but no more than the number of jet at altitude.

Question #4, I know that contrails are formed under certain weather conditions and altitudes. However, there are times when conditions do not exist for contrails to persist?
Then they will not persist. The problem here is that it is incredibly difficult to know what the humidity is at a specific time, altitude and location. Humidity measurements are done by sending up a balloon every 12 hours from weather stations 300 miles apart, the balloon can be blown hundreds of miles in a random direction during its ascent. How can you get an accurate local humidity reading at a specific time and place from a balloon reading 6 hours ago and 300 miles away, when humidity can vary enough for contrails to form or not form in as little as half a mile (as you can see from the broken contrails), and humidity can vary by 50% over the course of a day?

Question #5, Certain contrails even look like they are laden with chemicals. You know the ones I mean. The ones that appear to drip by the weight of their own substance, mushrooming along the bottom edge of the trail. C’mon what’s in this stuff. It doesn’t even look like ordinary condensation to me?

They are called “pendules”, as seen in this pre-1991 photo, and described by Schaefer and Day in 1981. When a plane flies through the air at 500mph it creates wake turbulance, which is made up of wake vortices, (whirlpools of air), at regular intervals. These vortices make the contrail clump up in areas of greater and lesser density. In a dense persistent contrail, the vortices will produce the clumping pendules seen in the first photo. If the contrail is thin or not persistent, then they can leave interesting patterns which can resemble smoke rings. The type and visibility of the vortices will depend on the the size, shape and speed of the jet, as well as the turbulence and density of the air it is moving through.

Question #6, Speaking of abnormal, I have seen jets emitting contrails that are dark in appearance. I assumed that it might be the lighting conditions until I saw the black and white contrails side by side – check out this video?
I covered this in the “dark lines” article. It is the lighting conditions, the dark contrail is in shadow, and when you see contrails “side by side”, the lighter contrail could well be ten miles behind (or a mile above) the darker contrail, and so not in shadow.

Question #7, Another interesting aspect to these dark trails is that the material drifts to the ground in clouds that resemble the black smoke from a nearby fire. I have observed this process several times in the fall. I haven’t seen them since the beginning of the year?
Precipitation falling from clouds will look dark if it is in shadow, which is probably will be if the shadow is caused at sunset by a hill or cloud bank.

Question #8, And then there’s the other trails that appear to swallow up other trails and clouds. One of my YouTube videos shows this quite clearly. My first impression was that someone had a HUGE washcloth and scrubbed a portion of the sky. And then I saw jets going through the cloud mass and the contrails that were left created lines in the mass that expanded and left the cloud in sections.
This effect was observed in 1944, it’s basically a distrail, which is the opposite of a contrail, the cloud contains moisture, and the added moisture, particulates and turbulence of the jet passing through makes the amount of moisture in the air too great for it to exist as a cloud, so it precipitates as snow or rain. This wipes away the cloud where the contrail has been. This can also happen with cloud layers that are below the contrail, as precipitation from the contrail falls on the cloud layer. This is also known as “hole punch clouds” and “fallstreak holes“. Distrails can combine with the vortices of question 5, as in the photo on the right.

I hope I’ve answered all these questions. If you feel there is still something unclear, or you have extra questions, then please leave a comment below.

*UPDATE* Some more questions were raised in the comments, and I’ll add them here, with answers.

Question #9, On your website you have a picture of one jet leaving a “chemtrail” with another jet at the same altitude in the background is not leaving one. I have seen jets side by side and one leaving a normal contrail and another leaving a chemtrail?

See this post for a full discussion.

There are two possibilities. either the jets are not at the same altitude, and just look like they are because of the viewing angle, or they have different engines with different exhaust characteristics. The more efficient an engine is, the more likely it is to leave a lasting contrail, as there is more water in the exhaust. The photo on the right shows an Airbus A340 (maiden flight: 1991) on the left, leaving contrails, and a Boeing 707 (maiden flight: 1957) not leaving contrails. Both are flying at 33,000 feet (part of a German test to study contrail formation), but the newer engines of the A340 produce more water vapor.

Questions #10, How do you explain pictures of aircraft spraying chemtrails from ports other than the engines?
It’s an optical illusion. The contrails come from the engines. Engine exhausts contain a lot of water, which (combined with the water in the air), condenses, freezes and causing the contrail. Because it’s hot when it exits the engine, it takes a fraction of a second to condense and freeze (in 40 below temperatures). So it begins to freezes about 100 feet behind the engines, which makes it look like it’s coming from the ends of the tail section. This illusion is stronger on a shorter two-engine plane – look at the inner engines on the picture on the right. Since it’s a four engined 747 (240 foot long), the contrails form before the tail section, but with shorter planes such as a 767-300 (180 foot long) the contrails would be forming about at the tips of the tail section when viewed from below (although they are actually well underneath the tail, as you can see in the close-up).

In very humid conditions, the turbulence caused by the aircraft itself can cause moisture in the air to condense, and hence freeze. This happens in areas of low pressure above the wing, and in the wingtip vortices, so you can get what looks like a solid sheet of contrail from the wing, and thin streamers from the wing tips (and maybe the tail), combined a bit further back with the engine contrails, as in the photo on the right. These low-pressure wing contrails can form at any altitude, given the right humidity, and account for the tales of planes landing “still spraying”.

Question #11, How do you explain scientists testing the fallout and finding aluminum, barium, nano particles, fungus, molds, viruses, etc in the mix?
They did not test contrails, they just tested some stuff they found on the ground, with no indication that it was connected with contrails (it would take several days for aerosolized matter to reach the ground, and by that time it would have been spread hundreds of miles from the original site). Most of the things they claim to have found are things that naturally occur in air and dirt.

185 comments on “Contrail Gaps and other Questions”

  1. Captfitch:

    Are you generalizing the troposphere into the stratosphere?

    I hope not.

    The “troposphere” is the rough, non-laminar bit you pilots try to avoid. And do, for most of any journey

    The “tropopause” is the point where the ambient air temperature is at its lowest, but is otherwise hard to see. Except that you might see it as a layer where cirrus (and aircraft trail ice) begin to evaporate as they fall into warmer air.

    Above that, in the “stratosphere”, the ambient air temperature gets warmer with increasing height. (From a low of down to -80 degrees F!)

    The tropopause height varies oblately between 18,000 feet over the poles to 45,000 feet over the equator, approximately, so really we’re both correct. It depends on the route you take. 🙂

    The air journey I’m most familiar with is the north/south one between England and the Canary Isles, which starts above the tropopause, after the climb, but ends beneath it, before the descent.

  2. JazzRoc is a brit? Wtf, damn limey ass. genesis fan? Yes? King crimson?…how about This Heat? the 801 live?

    So who is “right” about this troposphere/tropopause/stratosphere nonsense.
    You guys dont seem very credible.
    I’d hate for any plane I’m riding in to be piloted by dumb and dumber.

  3. TROPO-
    The troposphere is the lowest portion of Earth’s atmosphere. It contains approximately 75% of the atmosphere’s mass and 99% of its water vapor and aerosols.
    The average depth of the troposphere is approximately 17 km (11 mi) in the middle latitudes. It is deeper in the tropical regions, up to 20 km (12 mi), and shallower near the poles, at 7 km (4.3 mi) in summer, and indistinct in winter. The lowest part of the troposphere, where friction with the Earth’s surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km (1.2 mi) deep depending on the landform and time of day. The border between the troposphere and stratosphere, called the tropopause, is a temperature inversion.[1]

    STRATO-
    The stratosphere is the second major layer of Earth’s atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth’s surface, which is cooler higher up and warmer farther down. The border of the troposphere and stratosphere, the tropopause, is marked by where this inversion begins, which in terms of atmospheric thermodynamics is the equilibrium level. The stratosphere is situated between about 10 km (6 miles) and 50 km (31 miles) altitude above the surface at moderate latitudes, while at the poles it starts at about 8 km (5 miles) altitude.

    PAUSY-
    The tropopause is the atmospheric boundary between the troposphere and the stratosphere. Going upward from the surface, it is the point where air ceases to cool with height, and becomes almost completely dry. More formally, it is the region of the atmosphere where the lapse rate changes from positive (in the troposphere) to negative (in the stratosphere). This occurs at the equilibrium level (EL), a value important in atmospheric thermodynamics. The exact definition used by the World Meteorological Organization is:
    the lowest level at which the lapse rate decreases to 2 °C/km or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2 °C/km.
    The troposphere is the lowest of the Earth’s atmospheric layers and is the layer in which most weather occurs. The troposphere begins at ground level and ranges in height from an average of 11 km (6.8 miles/36,080 feet at the International Standard Atmosphere) at the poles to 17 km (11 miles/58,080 feet) at the equator. It is at its highest level over the equator and the lowest over the geographical north pole and south pole. On account of this, the coolest layer in the atmosphere lies at about 17 km over the equator. Due to the variation in starting height, the tropopause extremes are referred to as the equatorial tropopause and the polar tropopause.

  4. What this means guys…
    is that the TROPO-PAUSE would actually be the MOST LIKELY,(and most of the time),
    place that one should have any sort of Persistent Contrails.

    I find it rather ironic the INVERTED progression in air temp from warmer to cool(troposphere) and then from cool to warm(stratosphere) wasnt one of the first things mentioned when I found this board.
    (take a hint)

    If I was going to explain Persistent Contrails to anyone this would be one of the first points to explain.
    But, for me, as well as I’m sure for others, it opens up new questions….and possible inconsistencies.

    If the data for LA airspace at the time of massive Contrail Cirrus the “tropopause” should correspond with correct humidity/temp and documented flight elevations in order for “everything to be ‘normal'” as far as
    contrail science is concerned.

  5. Thats an interesting question, if you look in Wikipedia, it says:

    http://en.wikipedia.org/wiki/Tropopause

    Most commercial aircraft are flown below the tropopause or “trop” if at all possible to take advantage of the troposphere’s temperature lapse rate. Jet engines are more efficient at lower temperatures.

    But then it also says:

    http://en.wikipedia.org/wiki/Stratosphere

    Commercial airliners typically cruise at altitudes of 9–12 km in temperate latitudes, in the lower reaches of the stratosphere.[2] They do this to optimize jet engine fuel burn, mostly thanks to the low temperatures encountered near the tropopause. It also allows them to stay above any hard weather, and avoid atmospheric turbulence from the convection in the troposphere. Turbulence experienced in the cruise phase of flight is often caused by convective overshoot from the troposphere below.

    So there’s some confusion there. The confusion is perhaps caused by the loose definition of the regions. Where and how big is the tropopause exactly?

    Have a look at the current Skew T plot for Vandenberg CA:

    http://weather.unisys.com/upper_air/skew/skew_KVBG.html

    http://contrailscience.com/skitch/Unisys_Weather__Current_Skew_T_Plot_for_Vandenberg_CA_%28VBG-74606%29-20100310-103342.jpg

    Note the temperature (white line on the right) is in a diagonal scale (the blue lines). It drops at about the expected lapse rate up to around 11,000m (36,000 feet), and then is basically stable (45 degrees) up to 16,000m (52,000 feet). Based on that, it would see the troposphere extends up to 36,000 feet (FL360, like captfitch said, is the standard Tropopause). Many commercial flights are below 36,000 feet, some are above.

  6. Ok. So what does “engines are more efficient in colder temps” mean exactly.
    For the engines to be “efficient” in the area near the tropopause
    they are also more likely to create contrails, persistent contrails and change the weather.
    Another Catch 22.

  7. For all intensive purposes I’m right. We’re not looking at contrail pics over Antarctica. The one’s we see are in the middle latitudes and I’m telling you that they are being created in the troposhere and occasionally the tropopause.

    And turbine engines (all engines really) operate more efficiently at cold temps because the temperature essentially tricks the engines into believing they are operating at a lower altitude and higher pressure. The airframe likes to be high, the engines like to be low and both things like to be cold.

  8. Seems there’s research being done on whether the reduction of sulphur in aviation fuel may reduce the growing occurrence of persistent contrails from commercial airliners. You only have to google ‘sulphur contrail cirrus’ to find loads of scientific research published on the web. This suggests that some scientists far from denying the existence of persistent contrails are worried about the negative effects of contrail induced cirrus – mainly in relation to global warming. Why do chemtrail believers find it so hard to see the significant relationship between budget air travel and increase in contrails? They always say chemtrails began in the 80s/mid-90s which also corresponds with the invention of the internet and digital photography!

  9. Please check British Constitution Group’s Andrew Johnson – ‘Evidence in Plain Sight’ recycling the same old ‘evidence’ only this time he’s linking ‘chemtrails’ to 9/11.

  10. ANON:Why do chemtrail believers find it so hard to see the significant relationship between budget air travel and increase in contrails?

    First of all to say “chemtrail believers” is an massive oversimplification.
    Could you imagine trying to make the same generalizations about groups of people,
    like lets say “christian ‘believer’s”
    or “UFO believers”…??? well? could you?

    No, you cannot.
    If you call me a “chemtrail believer” I’ve already make the case that a “CHEMTRAIL” is also by my definition
    also a Persistent Contrail.
    So I’ve basically dis-proven your assumption.

  11. CCTYF:

    I find it rather ironic the INVERTED progression in air temp from warmer to cool (troposphere) and then from cool to warm (stratosphere) wasn’t one of the first things mentioned when I found this board.

    Well I’ll bet you I’ve mentioned it on at least a half-dozen occasions. It’s a very telling point, and when you understand it, it changes your perception of high-altitude trail photos, and your interpretation of all the “evidence” w.r.t. “chemtrails”.
    As for being a “Brit” – I’m a Brit like Tom Jones or Richard Burton is or was a Brit: absent.

    Ok. So what does “engines are more efficient in colder temps” mean exactly? For the engines to be “efficient” in the area near the tropopause they are also more likely to create contrails, persistent contrails and change the weather. Another Catch 22.

    Now you’re making more sense.
    You must have noticed your car’s performance increasing in cold foggy conditions. Engines just love high-pressure humid intake air. But aircraft airframes just hate flying through choppy tropospheric air at high speed.
    It isn’t impossible to load up Air Traffic Control with the additional responsibility of managing the avoidance of dense trail-making by slotting flights above or below the offending conditions.
    If you are concerned about the (3.5%) attributable increase to Global Warming due to air travel then perhaps you could action for this improvement.

  12. Anonymous:

    Please check British Constitution Group’s Andrew Johnson – ‘Evidence in Plain Sight’ recycling the same old ‘evidence’ only this time he’s linking ‘chemtrails’ to 9/11.

    And HAARP. And almost anything else:

    http://contrailscience.com/chemtrails-the-best-evidence/comment-page-3/#comment-43077

    Anonymous, once you have “evidence” you must also have the means to interpret it. This requires education, understanding, AND experience.

  13. http://www.grida.no/publications/other/ipcc%5Fsr/?src=/Climate/ipcc/aviation/032.htm
    “In the future, aircraft with more fuel-efficient engines will produce lower exhaust temperatures for the same concentration of emitted water vapor, hence will tend to cause contrails at higher ambient temperatures and over a larger altitude range.”—-IPCC

    You must have noticed your car’s performance increasing in cold foggy conditions

    Sorry bloke, you’re thinking of a different laditude~~

    Never had a car!!! Only bicycle! and even when I lived in new england.
    I’ve never lived anywhere with “cold foggy conditions” ironically. never.

    The LOS ANGELES increase in persistant contrail cirrus has grown substantially. You would
    know if you lived here. But, you dont. So dont bother speculating.

  14. If you are concerned about the (3.5%) attributable increase to Global Warming due to air travel then perhaps you could action for this improvement.

    Yo, limey, the jury will be out for a LOOOOOOOOONG time on that one.
    Your “3.5percent” figure is garbage. meaninglesss.

  15. Anonymous:

    This suggests that some scientists far from denying the existence of persistent contrails are worried about the negative effects of contrail induced cirrus – mainly in relation to global warming.

    NO scientists anywhere have ever denied “the existence of persistent contrails”. They have been known by ALL ATMOSPHERIC SCIENTISTS to exist at least since 1943, when they adversely affected the US Army’s bombing campaign over Germany in WW2.

    They are NOT worried about the “negative effects of contrail induced cirrus – mainly in relation to global warming”. They KNOW (because they have measured and calculated it) that the effect of aviation is a 3.5% contribution to global warming.

    The concern they have is for the oxides of sulfur and nitrogen generated by combusting aviation kerosine. This is thought to migrate through the high stratosphere to the polar regions, where it contributes to the holes in the ozone layer which allow through the high-energy ultra-violet radiation known to cause skin cancer.

  16. CCTYF:

    Yo, limey, the jury will be out for a LOOOOOOOOONG time on that one.
    Your “3.5percent” figure is garbage. meaninglesss.

    Aviation’s total climate impact is some 2-4 times that of its CO2 emissions alone (excluding the potential impact of cirrus cloud enhancement). This is measured as radiative forcing. While there is uncertainty about the exact level of impact of NOx and water vapour, governments have accepted the broad scientific view that they do have an effect. Accordingly, more recent UK government policy statements have stressed the need for aviation to address its total climate change impacts and not simply the impact of CO2.
    The IPCC has estimated that aviation is responsible for around 3.5% of anthropogenic climate change, a figure which includes both CO2 and non-CO2 induced effects.
    – The Intergovernmental Panel on Climate Change (IPCC).

    The above statement is both TRUE and CONTRAIL SCIENCE.

    Thanks for providing the “chemtrail pseudoscience” to work against.

  17. yes, here I’m also quoting the IPCC which is not god, nor the truth.

    http://www.grida.no/publications/other/ipcc_sr/?src=/Climate/ipcc/aviation/032.htm

    In the future, contrail cloudiness and radiative forcing are expected to increase more strongly than global aviation fuel consumption because air traffic is expected to increase mainly in the upper troposphere, where contrails form preferentially, and because aircraft will be equipped with more fuel-efficient engines. More efficient engines will cause contrails to occur more frequently and over a larger altitude range for the same amount of air traffic. For the threefold increase in fuel consumption calculated for a 2050 scenario (Fa1), a fivefold increase in contrail cover and a sixfold increase in radiative forcing are expected. The contrail cover would increase even more strongly if the number of cruising aircraft increases more than their fuel consumption. For other 2050 scenarios (Fc1 and Fe1), the expected cirrus cover increases by factors of 3 and 9, respectively, compared to 1992. Higher cruise altitudes will increase contrail cover in the subtropics; lower cruise altitudes will increase contrail cover in polar regions. Future climate changes may cause further changes in expected aircraft-induced cirrus cover.

    The future aerosol impact of aviation will increase with fuel consumption. The trends depend on future fuel-sulfur content, engine soot emissions, and the efficiency with which fuel sulfur is transformed into aerosol behind the aircraft.

    Aerosol microphysical and chemical processes are similar in subsonic and supersonic aircraft plumes. Aerosol properties will differ because soot emission levels, aerosol formation potential, and plume dilution properties vary with engine type and atmospheric conditions at cruise altitudes. Significant increases in stratospheric aerosol are expected for the operation of a large fleet of supersonic aircraft, at least for non-volcanic periods.

  18. (excluding the potential impact of cirrus cloud enhancement)

    In case you missed something, WEATHER EFFECTS are the prime motivating unknown here.
    To equate any other ground based co2 emissions to Jet engines in the troposphere is irresponsible.

  19. CCTYF:

    I’m also quoting the IPCC which is not god, nor the truth.
    But it’s closer to either than you’ve been so far.

    In the future, contrail cloudiness and radiative forcing are expected to increase more strongly than global aviation fuel consumption [snip] increases in stratospheric aerosol are expected for the operation of a large fleet of supersonic aircraft, at least for non-volcanic periods. fuck the IPCC and fuck any increase in air travel. Its all just insanity.
    It’s amazing, isn’t it, that passing PEAK OIL seems to have made no difference to either their or your statements?

    In case you missed something, WEATHER EFFECTS are the prime motivating unknown here.
    We all thought you hadn’t noticed. Welcome to contrail science! 🙂

    To equate any other ground based CO2 emissions to Jet engines in the troposphere is irresponsible.
    Why is that? Haven’t you noticed that you have just contradicted yourself?

  20. BUT, you never mentioned this…which, HAS CHANGED…

    “An engine performing with a higher overall propulsion efficiency causes plume conditions which during mixing reach a higher relative humidity for the same ambient temperature, thus causing contrails also at a higher ambient temperature.”

    Potential of lowering the contrail formation of aircraft exhausts by engine re-design
    http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VK2-4RDR1J7-1&_user=10&_coverDate=09%2F30%2F2008&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ab895cc7db0eb1f9418340634928b7ff

  21. The issue in question for contrail cirrus isnt so much Just the “pollution” but the special effects artificial contrail cirrus
    have on the whole climate-system and cloud formation itself.

  22. It’s amazing, isn’t it, that passing PEAK OIL seems to have made no difference to either their or your statements?

    where are you going with that one JazzRoc? I could take wild guesses.
    Whats your take?

  23. CCTYF:

    BUT, you never mentioned this… which, HAS CHANGED: “An engine performing with a higher overall propulsion efficiency causes plume conditions which during mixing reach a higher relative humidity for the same ambient temperature, thus causing contrails also at a higher ambient temperature.”
    I didn’t mention it because it has already been mentioned here. The first instances of this occurred in the late sixties with the development of turbofan engines. These aren’t going to go away. Nor are they going to get much “worse”.

    Potential of lowering the contrail formation of aircraft exhausts by engine re-design
    Isn’t a good idea when you look at the efficiency reductions involved. Especially when you compare it with my suggestion to arrange that aircraft are simply routed to AVOID offending layers – without any loss in operating efficiency.

    The issue in question for contrail cirrus isnt so much just the “pollution” but the special effects it has on the whole climate-system and cloud formation itself.
    It’s been quantified, hasn’t it, at 3.5%?

    You must realize that ALL anthropogenic activity is relevant? In other words, it is just as important to limit forest fires, stubble burning, “slash-and-burn” farming, tundra warming, fossil fuel power generation, manufacturing effluents, petrochemical effluents, greenhouse gases, oil tanker exhaust emissions, mass transportation and private car exhaust emissions, ALL 96.5% of the whole, as it is to limit the 3.5% due to air travel?

    In the atmosphere they are ALL going to be ADDITIVE.

    And subject to VOLCANIC EMISSIONS which we can’t do anything about.

  24. CCTYF: What’s your take?

    BY 2050 the West is going to be lean, mean and hungry, while the East is going to pollute like we once did. The West will no longer be in control.

    Cheap air travel is going to fade into the past, and air travel as a whole is going to stabilize to not much more than the present level – but centred around the Pacific rather than the Atlantic.

    The Earth will be more than two degrees warmer, the sea level will have risen six feet.

    Some tipping points; tundra methane, clathrate methane, Arctic ice cover, Antarctic Ice Shelf motion, ocean acidity, could render my predictions wildly inaccurate.

    Aviation AGW will no longer be ours to argue about. We’ll be proliferating nuclear power stations all over.

    It’ll be a gas…

  25. my suggestion to arrange that aircraft are simply routed to AVOID offending layers – without any loss in operating efficiency.

    why isnt this done already?
    cost of extra fuel waste?

    The issue in question for contrail cirrus isnt so much just the “pollution” but the special effects it has on the whole climate-system and cloud formation itself.
    It’s been quantified, hasn’t it, at 3.5%?

    Actually, from my understanding, the 3.5% figure is in regards to the POLLUTION, not the EFFECTS of
    CONTRAIL CIRRUS.
    Are we reading the same information differently?
    The way ARTIFICIAL CLOUD COVER effects the climate/global environment is an altogether different issue than
    the pollution from aerosols etc…
    We’re talking weather patterns/ amount of sunlight/ evaporation rate.
    Remember, this “breakthrough” only came AFTER 9/11.
    It was in 2001 that the issue really made its biggest statement.
    The calculations previous this downing of all us airplanes gave a UNIQUE new look into whats going on.
    They didnt expect what they found.

    At least thats the information that I’ve read. From NASA as well.

  26. Good questions.

    The 3.5% figure is the IPCC estimate for the TOTAL CLIMATE EFFECT from air traffic, not just “pollution”. See here, where the various effects are broken down.

    http://www.grida.no/publications/other/ipcc_sr/?src=/climate/ipcc/aviation/064.htm

    For the 1992 aviation scenario (NASA-1992*), radiative forcing of climate change from aircraft emissions (gases and aerosols) is estimated to be +0.05 W m-2, which is about 3.5% of total anthropogenic radiative forcing as measured against the pre-industrial atmosphere of +1.4 W m-2 for combined greenhouse gases and aerosols (and +2.7 W m-2 for greenhouse gases alone). The components of aircraft-induced radiative forcing are as follows:

    CO2, +0.018 W m-2;
    NOx, +0.023 W m-2 (via ozone changes) and -0.014 W m-2 (via methane changes);
    contrails, +0.02 W m-2;
    stratospheric H2O, +0.002 W m-2;
    sulfate aerosol (direct effect), -0.003 W m-2;
    black carbon aerosol (soot), +0.003 W m-2.

    Changes in “natural” cirrus clouds caused by aircraft may result in negligible or potentially large radiative forcing; an estimate could fall between 0 and 0.04 W m-2. Uncertainty estimates, typically a factor of 2 or 3, have been made for individual components and are intended to represent consistent confidence intervals that the radiative forcing value is likely (2/3 of the time) to fall within the range shown. The uncertainty estimate for the total radiative forcing (without additional cirrus clouds) is calculated as the square root of the sums of the squares of the upper and lower ranges of the individual components.

    Projection of subsonic fleet growth to 2015 (NASA-2015* scenario) results in a best estimate for total aircraft-induced radiative forcing of +0.11 W m-2 in 2015-about 5% of IS92a projected radiative forcing from all anthropogenic emissions that year.

    Note there’s some uncertainty there, but still scientists are pretty sure it’s in the ballpark. Estimated to rise to 5% by 2015.

    The Pan Evaporation Rate decline you mention is thought to come mostly from particulates in the atmosphere from pollution. Jet flight does not contribute much to this. It’s linked to “Global Dimming”, which has actually been DECREASING in the last ten years. So can hardly be related to any supposed increase in contrails.

    The 9/11 observations have since been re-analysed, and are not as significant as once thought, based on the actual weather at the time (it was an unusually sunny day in the US, as I’m sure you remember). See:

    http://www.flightglobal.com/blogs/future-proof/2009/05/exclusive-911-not-to-blame-for-climate-effect.html

    According to US scientists who studied US skies after the September 11 terrorist attacks in 2001, the absence of artificial clouds caused by the grounding of all civil aircraft triggered variations in the earth’s temperature range by 1.1 degrees Celsius (2 degrees Fahrenheit) each day.

    But follow-up work by a number of scientists working independently have shown that the observed change in the daily temperature range or DTR was likely a statistical quirk associated with the weather and that contrails by themselves are likely only to have a very minor effect on DTR.

  27. CCTYF:

    Why isn’t this done already? Cost of extra fuel waste?

    I don’t know. I suggest it is because the airlines have no external compulsion upon them to increase their flight crews’ work rate.

    During daylight (at least), a rearward-facing videocam could provide an instant view of the trail being made. If it turned out to be heavy, the crew could ask ATC for a different height to fly at.

    By comparing notes with all the aircraft on the panel, ATC could form a pretty good picture of supersaturated layers. It may even be possible to develop the software to put these on screen.

    It’s tricky because it is the aircraft engines themselves which are the most sensitive detectors of supersaturation.

    Moving the aircraft’s cruise height will hardly affect its efficiency at all.

    Changing the internal design of modern turbofans to produce such a drastic reduction of efficiency (as suggested by the paper you quoted) would put the aircraft industry in a whole new world of hurt. In fact it’s laughably unlikely.

  28. For all intensive purposes I’m right.

    Sorry, but “intensive purposes” is really funny.

  29. JazzRoc

    I’m wondering why you appear to be arguing with me.

    ‘NO scientists anywhere have ever denied “the existence of persistent contrails”. They have been known by ALL ATMOSPHERIC SCIENTISTS to exist at least since 1943, when they adversely affected the US Army’s bombing campaign over Germany in WW2.

    They are NOT worried about the “negative effects of contrail induced cirrus – mainly in relation to global warming”. They KNOW (because they have measured and calculated it) that the effect of aviation is a 3.5% contribution to global warming.’

    I am certainly not arguing with you. I am making the same point you are.

  30. CTYForg:

    ‘First of all to say “chemtrail believers” is an massive oversimplification.
    Could you imagine trying to make the same generalizations about groups of people,
    like lets say “christian ‘believer’s”
    or “UFO believers”…??? well? could you?

    No, you cannot.
    If you call me a “chemtrail believer” I’ve already make the case that a “CHEMTRAIL” is also by my definition
    also a Persistent Contrail.
    So I’ve basically dis-proven your assumption.’

    Commonly people of faith as are referred to as ‘believers’. You continue to have ‘faith’ that there is something nefarious about persistent contrails despite all the readily available science that disproves your hypothesis.

  31. Anonymous:

    I am certainly not arguing with you. I am making the same point you are.

    I wasn’t sure you were, sorry.

    I just wished to stress that the full science of anthropogenic changes to the atmosphere was yet to be fully understood, and that the incompletely-understood part was that of the migration of combustion products to the poles and their effect on the “ozone hole”.

  32. I just wished to stress that the full science of anthropogenic changes to the atmosphere was yet to be fully understood, and that the incompletely-understood part was that of the migration of combustion products to the poles and their effect on the “ozone hole”.

    No problem I think I came into the middle of an in depth discussion with a general observation.

  33. I’ve just had a look at your blog, JazzRoc and had to let you know that I found Andrew Johnson’s comments breathtakingly arrogant. He seems to think his ‘computer science course’ qualifies him to argue with people who have spent much of their lives studying the weather. I have seen his presentation on Youtube – he cites all the same spurious evidence as everyone else on the chemtrail conspiracy bandwagon and has discovered nothing new. His entire hypothesis is based on the false assumption that cirrus clouds cannot form from contrails. His only ‘proof’ is to say that none of the agencies he contacted were able or prepared to tell him which long haul flights go over his house. There is absolutely no doubt in my mind that the aviation authorities think his argument is too bonkers and unsubstantiated to merit a response.

    I think your blog and this website is great and I can see that some people on here have been open minded enough to accept your reassurances. Those that struggle to absorb the science may find it easier and less humiliating to write you off as employees of NASA or operatives or whatever. I attempted to explain contrail science to my partner, showing him among other things the simple explanation on the UK Science Museum’s website. But it seems anything that is not on the website of a chemtrail conspiracy theorist is written off as ‘disinformation’. I’m interested in this subject only because I’m living with someone who refuses to do any research other than look at conspiracy websites. He has spent a whole year obsessing about being ‘sprayed’ by the government – this dominates every trip we make outside of the front door. He becomes aggressive with me when I try and suggest an explanation. I think his time would be better spent researching the dangers to mental health from long term marijuana abuse.

  34. A note on “effinciency”:

    I haven’t really looked into effiency that much but I can tell you that altitude has everything to do with how “efficient” an engine is based on one simple fact. The higher we go the less fuel our engines use for a given airspeed. The fuel flow may be 1200 pounds per hour at FL200 but will be down to 600 pounds per hour at FL430. So the higher we go the better- the problem is the wings run out of air at higher altitude.

    I don’t know if that’s a good definition for efficiency, however, but it works for me.

    What’s red and smells like blue paint?

    Red paint

  35. Uncinus:

    JazzRoc: “Moving the aircraft’s cruise height will hardly affect its efficiency at all.”
    You got some numbers to back that up?

    No. Not to hand. I’m an old-age pensioner on a sub-tropical island now – happy just to possess a modicum of clothing, and a micro.

    My experience tells me it’s a compromise between flying through colder air (that would be AT the tropopause – making the engine more efficient) and flying through the warmer but thinner air at higher altitudes (reducing the drag on the airframe), with a final upward limit on the altitude where there is insufficient wing area to provide efficient lift, and the angle of attack of the wings increases past the optimal. I believe captfitch would say the same.

    For actual numbers it would be better to find information from the manufacturers (such as Boeing), though I suspect they might not be too keen to release it, for it really is their proprietary information.

    I do know such information is different for each and every aircraft type, and different even for the same, but differently-engined, aircraft type, so I’ll have to stick with my original statement… sorry.

    Flying AT the tropopause guarantees engine efficiency (and sometimes the densest of contrails), whilst flying above it reduces engine efficiency – but reduces drag (but not necessarily the chance of producing dense contrails). and may increase flight efficiency in general.

  36. Theoretically thought here must be an optimum altitude – or at least an optimum arc of altitudes for each trip.

    It varies with the weight of the plane. As the plane burns fuel and become lighter it requires less lift, so can fly in thinner air. See:

    http://en.wikipedia.org/wiki/Step_climb

    The altitude that provides the most fuel-efficient cruise at the start of a long flight, when the aircraft is fully loaded with fuel, is not the same as the altitude that provides the best efficiency at the end of the flight, when most of the fuel aboard has been burned. This latter altitude is usually significantly higher than the former. By climbing gradually throughout the cruise phase of a flight, pilots can make the most economical use of their fuel.

    Which implies that climbing or descending a few thousand feet to avoid making contrails in not going to be economically appealing to the airlines.

  37. I could be really wrong here but I’m almost positive we can’t make it to the stratosphere. I believe we spend most of our time in the troposphere and tropopause. The tropopause is pretty high up and pretty thick in our latitudes. The wings would run out long before we hit the temperature increase of the stratosphere. And yes we do step climb but typically we climb as high as the book says we can go for that weight, burn off fuel and then climb some more. And no- we would never change altitude to decrease contrail formation because then we would all be funneled into the same altitudes, thus increasing an already congested sky. I’d rather fly through contrails than other airplanes.

  38. captfitch:

    I’d rather fly through contrails than other airplanes.

    Indeed. 🙂

    I wasn’t suggesting it was an easy solution – just a possible one.

  39. “I’d rather fly through contrails than other airplanes.”

    But, aren’t you afraid of getting poisoned from all those chemicals? Or did the Government inoculate all the pilots and that’s why you’re not worried. 😉

  40. Shhhh- the first rule about being a pilot is not talking about the inoculations. The second rule is no talking about flight club.

  41. I could be really wrong here but I’m almost positive we can’t make it to the stratosphere. I believe we spend most of our time in the troposphere and tropopause. The tropopause is pretty high up and pretty thick in our latitudes.

    I think there’s some usage of terms confusion here. I read the definition of the tropopause as just being the boundary between the troposphere and the stratosphere, and not an actual distinct layer itself. It’s just a specific altitude, not a region you can be “in”. Hence if you are not in the troposphere then you are in the stratosphere.

  42. yeah- I’ll agree with that. I guess I’ve just never experienced a temperature increase with an increase of altitude (besides an inversion).

  43. According to Standard Atmosphere, the temp is constant up to 20,000m (65,000 feet). Which seems to match the soundings, more or less.

    I could see how from looking at that diagram you might assume the tropopause was the region with constant temperature (11-20km). The text that accompanies it says:

    We live in the troposphere which means “the area of change”. In the troposphere the temperature decreases with increasing altitude at a rate of 1.98°C or 3°F/1000 ft. The troposphere extends up to 60,000 ft. over the equator but only to about 30,000 ft. over the poles. At that altitude it becomes the tropopause where the air temperature is fairly constant between – 50 and -55°C. Above the tropopause, which is about 30,000 ft. deep, is the stratosphere which extends to about 50 miles (80 kms.). There is no weather in the stratosphere and indeed there is little weather above 35,000 ft. One of the joys of flying is that on the dullest day one can break out into bright sunlight if you climb high enough.

    http://www.tc.gc.ca/civilaviation/cam/tp13312-2/section2/atmosphere.htm

  44. Here is a random question that I am curious about but not sure where to ask it:

    Why doesn’t every contrail get spun and distorted by the wing vortices?

  45. I’d written above:

    The type and visibility of the vortices will depend on the the size, shape and speed of the jet, as well as the turbulence and density of the air it is moving through.

    It would also depend on the local wind direction.

    All contrails do get spun to some degree by the vortices (not just wingtip vortices). You can usually see this as a twist in the contrails between where it starts and where it’s at full width.. But if the air is locally less turbulent and the plane going slower then the result is going to be smother with less instabilities.

  46. You have to take perspective into account when looking at these images. When taken head on, from only a thousand feet above, the trails appear a denser, with the twist happening closer to the engine.

    If you take the above image, and project it to correct for foreshortening, you get a different picture (still can’t see the gap though, due to the angle).

  47. thanks for that- I should have known that every trail is effected by the vortices…

    What I really meant was why they didn’t all get super squiggly as in the “crow instability” style but as you mentioned that is probably a function of the surrounding air.

    That is a great pic as you can really see the trail spinning via the vortex.

    thanks.

  48. So, here’s the question that has truly puzzled me throughout this debate. Who are “they” that execute this “chemtrail” conspiracy. I get it that many believe it is “the government,” and I might even buy that as plausible if this were somehow limited to a relatively small number of sightings over government owned property. But here we are talking about a much larger scope than that. So who is involved in the conspiracy? If the government is doing this using commercial airplanes as the method of spreading these secret chemicals, how do they keep all the plane maintenance folks quiet? What about the hundreds of pilots who must be involved in order to release the chemical? Don’t you think, when the pilots are unhappy enough to go on strike that maybe a few of them would speak out to the press? And wouldn’t it be fairly easy to prove the release of all these chemicals by simple forensic science? There has to be some container on the plane that dispenses the chemicals and that container would be FULL of trace chemical at the very least. Actually there would be hundreds of these containers. And they would have to be filled by somebody. You don’t think one or a few of these people wouldn’t blow the lid off the whole mess for a few hundred bucks? Of course you could argue that some people have blown the whistle but nobody listens to them. If you argue that this is a second conspiracy, you introduce another mass of people who would know but for some reason keep their mouths shut.

    In the end, it is not just chemistry and physics that disprove the chemtrail conspiracy, but human psychology as well. For me that it is even the more compelling argument.

  49. All good points. It’s difficult to get into a rational conversation with a believer when it comes to points like these because it often goes like this:

    Non-believer: “I don’t believe in chemtrails because I’ve never seen any container in any plane that would hold some chemicasl.”

    Believer: “But I HAVE seen the trails in the sky! I don’t need containers when I can use my own two eyes to see the truth. Besides, they are obviously using xyz to spread the chemtrails.”

    But good luck!

  50. CHEMTRAILS ARE REAL. I’ve seen the planes up close with my own eyes. I’ve talked to ex military and air traffic personel. I know they pay you to operate on here. Stop wasting your time. And ours.. I’ve watched a plane fly 3 circles over my town and fly off in the direction it came. Military flights? You betcha! Tankers, no windows. Trust me I have close up pictures of these planes in the sky. Yes I have an insane zoom on my camera. 😉 A Msg to the people trying to disprove this “”Conspiracy”” you’re only F*cking you future selves over. WAKE UP.
    They have already ordered these planes down over Nigeria after the Flying aerosol can changed its call sign from civilian to military as it entered their airspace. That’s old news..

    If you truly believe what you are trying to prove give these links an honest look!! Thanks!

    http://www.fourwinds10.com/siterun_data/environment/humans/chemtrails/news.php?q=1246309936

    http://www.youtube.com/watch?v=QvsGuUtL0aM

    http://www.worldaffairsbrief.com/keytopics/Chemtrails.shtml

  51. Okay Pinecone, I’ve looked at your links, and I have a question. Your third link states:

    3) Contrails are always pure white and don’t exhibit much halo effect. Chemtrails have an oily glint to them, with pronounced rainbow-like color effects (reddish or pinkish tint) as the sun shines through.

    Now this seems entirely contrary to established science. It’s well known that contrails very similar optical properties to cirrus clouds.

    Can you explain why you believe this to be true? Especially given that the “what in the world are the spraying” video shows “chemtrails” as being pure white.

    Where’s the science?

  52. ..really??

    Sorcha Faal??

    REALLY? – please…you need to be a bit more discerning about your sources of info. “She” has made outrageous claim after outrageous claim for years…and not one has proven to be true.

    “her” credibility is highly suspect to say the least:

    http://www.abovetopsecret.com/forum/thread304918/pg1

    “she” is currently claiming the Oil rig in the Gulf was actually torpedoed by N. Korea.

    http://www.whatdoesitmean.com/index1367.htm

    Of course, you are welcome to buy her book:

    http://www.whatdoesitmean.com/battlebook.htm

  53. Hi !
    I am not in physics, neither in aerospace. I am skeptical. Sceptic see discuss the contrails & the chemtrails. Even if it is water vapour, I remain sceptical.
    With oil that pervades the Gulf, and the deadly gas, I wonder about issues. People are employed to collect waste on beaches. Without mask. Death arrives. What do BP & President?
    Spraying against the GW are made. Of the applications of what?
    Despite all your goodwill to answer questions, you did not discuss the possibility of spreading of poisons. Why?
    Death by respiratory disease rose from the 8th to the 3rd rank in 5 years! Why?
    Aircraft pilots have names and address. Why are they not talking… water?
    _____________________________________

    Je ne suis pas dans la physique, ni dans l’aéronautique. Je suis sceptique. Sceptique de voir discuter des contrails & des chemtrails. Même s’il s’agit de vapeur d’eau, je demeure sceptique.
    Avec le pétrole qui envahit le Golfe, et les gaz mortels, je me pose des questions sur les problèmes. Des gens travaillent à ramasser les déchets sur les plages. Sans masque. La mort arrive. Que font BP & le Président ?
    Des épandages contre le GW sont fait. Des épandages de quoi ?
    Malgré tout votre bon vouloir à répondre aux questions, vous n’abordez pas la possibilité d’épandage de poisons. Pourquoi ?
    La mort par maladie respiratoire est passée du 8ème au 3ème rang en 5 années ! Pourquoi ?
    Les pilotes d’avions ont des noms et adresse. Pourquoi ne viennent ils pas parler… de l’eau ?!

  54. Despite all your goodwill to answer questions, you did not discuss the possibility of spreading of poisons. Why?

    All thing are possible. But: Are they likely? Is there any evidence to support them?

    Death by respiratory disease rose from the 8th to the 3rd rank in 5 years! Why?

    Where are your figures? For 1999 to 2006 see:

    http://www.cdc.gov/nchs/nvss/mortality/lcwk9.htm

    They have remained in fairly constant order in that time. Respiratory disease at #4 with about 5% of deaths:

    1 Diseases of heart (heart disease)
    2 Malignant neoplasms (cancer)
    3 Cerebrovascular diseases (stroke)
    4 Chronic lower respiratory diseases
    5 Accidents (unintentional injuries)
    6 Alzheimer’s disease
    7 Diabetes mellitus (diabetes)
    8 Influenza and pneumonia
    9 Nephritis, nephrotic syndrome and nephrosis (kidney disease)
    10 Septicemia

  55. Hi !
    You say that there would be no cloud seeding and take up the toxicity of the chemtrails. Either. I would point out that although there is still this rumour, no head of State or Government has until then answered questions. These questions are at any point for its proper development and trade issues. And, as it is preferable for all (elected or not) to make friends rather than enemies, I do not understand this reluctance. Not wanting to respond or discuss politicians cache something.

    When it comes to respiratory diseases and deaths in ranking, I have not yet found missing data for 2007, 2008, 2009 and (there is) 2010.
    _______________________________________
    Vous dites qu’il n’y aurait pas d’ensemencement de nuages et niez jusqu’à la toxicité des chemtrails. Soit. Je ferai remarquer que malgré que subsiste cette ‘rumeur’, aucun chef d’Etat ou gouvernement en place n’a jusqu’alors répondu aux questions. Ces questions sont en tout point problématique pour le commerce et son bon développement. Et, comme il est préférable pour tout être (élu ou non) de se faire des amis plutôt que des ennemis, je ne comprends pas cette réticence. Ce non vouloir répondre ou en débattre des hommes politiques cache quelque chose.

    Pour ce qui est des maladies respiratoires et des décès en classement, je n’ai pas encore trouvé les données manquantes de 2007, 2008, 2009 et (s’il y a) 2010.

  56. @hemaurice, they admit weather modification. They also study contrails. To assume they are the same thing is absolutely the wrong way to go about understanding things. Assumptions are not based on knowledge. Cloud seeding uses silver iodide, dry ice, liquid nitrogen, cement dust, and maybe some other things if I haven’t read them all. Silver Iodide is the most common used. Why would politicians want to talk about cloud seeding? The scientists already cover these issues and politicians go over these issues with topics of global warming. And it amazes me people don’t consider the industrial emissions in terms of respiratory illnesses. Instead they search for the highest altitude and the least probable of contaminates. And there has been no evidence linking illnesses of people under flight paths to increased flights. Those illnesses can be from pollen, mold, smog, and household chemicals to any other range of things.

  57. Should heads of state be answering questions about every single conspiracy theory? If a head of state has not addressed a particular theory, then does that make it more likely to be correct?

    Officials in the US government have addressed the chemtrail theory many times. See for example the response from the US Air Force:

    http://www.af.mil/shared/media/document/AFD-051013-001.pdf

    The “Chemtrail” Hoax
    A hoax that has been around since 1996 accuses the Air Force of being involved in spraying the US population with mysterious substances and show various Air Force aircraft “releasing sprays” or generating unusual contrail patterns. Several authors cite an Air University research paper titled “Weather as a Force Multiplier: Owning the Weather in 2025” that suggests the Air Force is conducting weather modification experiments. The purpose of that paper was part of a thesis to outline a strategy for the use of a future weather modification system to achieve military objectives and it does not reflect current military policy, practice, or capability.
    The Air Force’s policy is to observe and forecast the weather. The Air Force is focused on observing and forecasting the weather so the information can be used to support military operations. The Air Force is not conducting any weather modification experiments or programs and has no plans to do so in the future.

    Or from the UK MOD:

    http://www.davidicke.com/forum/showthread.php?t=62515

    2. First let me try and put the issue into perspective, weblogs and other commentators sometimes refer to the vapour trails left by aircraft as ‘chemtrails’. These vapour trails should more correctly be termed condensation trails or ‘contrails’ and are formed by the water vapour from the engines of jet aircraft flying at high altitudes. To our knowledge, the only research on aircraft emissions undertaken by the Ministry of Defence was carried by the Met Office which was on the effect of aircraft emissions on the climate. The outcome of this research was published in an IPPC report called “Aviation and the Global Atmosphere 1999” (Available from Cambridge University Press). We are not aware of any further research conducted by or on the behalf of the Ministry of Defence.

    Why do you even think there has been an increase in respiratory disease if you have not figures?

  58. For respiratory diseases, I found this information over the Internet. But I still have no missing numbers.
    Brief.
    To which are declarations of the Oval Office, they must be the same as for BP “Motus !”
    Journalists banned in America in the Gulf !
    Chemtrails trusted and popular. Without control !
    Without control = genocide ?
    _________________________________________
    Pour les maladies respiratoires, j’ai trouvé cette information sur Internet. Mais je n’ai toujours pas les chiffres manquants.
    Bref.
    Pour ce qui sont des déclarations du bureau ovale, elles doivent être les mêmes que pour BP “Motus !”
    Journalistes interdit en Amérique dans le Golfe !
    Chemtrails approuvés et répandus. Sans contrôle !
    Sans contrôle = génocide ?!

  59. To me it looks like the shadow of the plane’s tail unit (mainly fin and rudder), cast on the fresh contrail.

    Imagine the sun standing low over the horizon (morning or evening, the video doesn’t say) in the direction the camera points to in the first close-up; it’s behind the plane. The contrail further behind is fully illuminated, it seems to be almost glowing. But most parts of the plane itself are shadowed, except for the lower front of the fuselage.

    A cloud in the right place below the plane would have shown a shadow of the whole thing including the one cast by the contrail.

    The only part of the plane that is above the contrail is the tail fin. If you look at images from the current four-engine passenger planes, this part is of considerable size.

  60. It looks like a gap. The contrail is just darkened and blends in with the background. Otherwise It is not affected.
    I can’t imagine a better explanation. Even if we assume that this is not an ordinary contrail, the effect would be no different.

  61. It is obviously a shadow. It does not cause a gap, merely a darken part of the contrail fades into background. The “gap” follows the plane with the same speed about 250 m/s, how else it would stay in exactly the same location relative the plane.

    Here is another example of shadow from the tail fin of Boeing E-3 Sentry in similar lighting conditions:

    http://contrailscience.com/wp-content/uploads/AWACS-1.jpg

    Compare it with a close up of the plane in your video at 0:33.

  62. “how can a shadow cause a gap?”

    You mean how can a shadow cause something viewed through many kilometres of atmosphere not to be visible?

    http://static.panoramio.com/photos/original/10206684.jpg
    Here is a picture of the moon viewed through earth’s atmosphere.

    There appears to be a few trillion tons of dark rock MISSING.
    The large GAP on the side of the moon is because it is in shadow and rayleigh blue light scattering makes us just see blue when in reality there is brownish grey rock.
    The intensity of the scattered blue light from the rest of the atmosphere is greater than the tiny amount of light scattered from the section of contrail in shadow

  63. Well spotted. Off the top of my head, it looks like the aircraft entered a holding pattern, and either only made 1 circuit, or descended below contrail height after 1 circuit.

  64. Hi Ars. have a careful look at the section on contrail simulations on this site.
    http://contrailscience.com/contrail-simulations/

    The path you photographed in the sky is not necessarily the path the aircraft flew at all.
    It is the simply where the contrail ended up after drifting with the wind.
    A plane flying in a perfect circle or oval pattern relative to the ground will leave a visible series of overlapping offset loops of contrail due to wind.
    http://contrailscience.com/wp-content/uploads/paperclip-contrails.jpg
    http://contrailscience.com/skitch/racetrack_contrail_simulator-20110119-181311.jpg

    In fact the fall streaks in your photos prove there is considerable wind shear and there were decently strong winds at the altitudes the plane you photographed was flying in.

  65. Hi Ars,

    As I can figure out from your second photo, it was taken from the point with approximate coordinates 37.199158800° -6.919800516° in southern direction. I have estimated that the elevation of the contrail self-crossing point is about 10° above horizon. Assuming the contrail altitude being about 10 km, I concluded that the contrail was about 60 km away from the camera, that is, it was above the ocean, not far from the Straight of Gibraltar and pretty close to the Rota Naval Station, which also is an aircraft base, according to Google Earth photos.

    Therefore, it is very likely that what you have witnessed was a military exercise rather that a civil aircraft in a holding pattern.

  66. Uncinus,

    I have reconstructed on Google Earth the contrail and the aircraft flight path from Ars Natura’s pictures and prepared a comment, but I do not see how to upload images on this site anymore. Was it disabled intentionally or unintentionally?

  67. In the case of Ars Natura coming back to this thread, I have reconstructed from his photos the contrail and the aircraft flight path on Google Earth.

    Firstly, I have found the exact locations of both viewpoints on Google Earth and checked them on Google StreetView. These viewpoints are about 16 km /10 miles apart. Secondly, I have added the photos, using identifiable ground features in them. Thirdly, for each added photo I iteratively have modelled the contrail so it would approximate the contrail image:

    It is said that about 10 minutes past between the first and the second photo. As seen from above, in this period of time the contrail (white line for the first photo and cyan line for the second one) was blown away in SSE direction by about 16 km /10 miles, that is, the upper air moved with the speed of a car, about 100 km/h / 60 mph. Taking the wind into account, I have deduced from the white model of a younger contrail a probable flight path of the aircraft (shown in red line):

    The wind direction and its speed is consistent with what can be deduced from the satellite images of the day:

    http://lance-modis.eosdis.nasa.gov/imagery/subsets/?project=&subset=AERONET_El_Arenosillo&date=11%2F16%2F2010

    In particular, the cirrus fall streaks emphasise the wind direction (along the coast, toward the Africa):

    http://lance-modis.eosdis.nasa.gov/imagery/subsets/?subset=AERONET_El_Arenosillo.2010320.aqua.250m

    The aircraft came in the direction from the Canary Islands and made a teardrop loop above the Gulf of Cádiz. It is not a predefined holding pattern for any of the nearby airports (Seville, Jerez and Faro). Perhaps, it was a cause of the “casualties” on the nearby US Naval Station Rota on the day: 🙂

    http://www.navy.mil/search/display.asp?story_id=57277

  68. PS
    After having watched air traffic in that region on flightradar24.com this morning, I think that the initial suggestion by MikeC about the aircraft entering a holding pattern is valid. I noted a few planes heading to the Faro International Airport (just beyond the left edge of the map in the previous post) from Europe did fly holding patterns in the Huelva area at altitudes of 6-7 km. This is a bit lower than the altitude I used in my contrail modelling. Reducing the altitude would result in scaling down the dimensions of the contrail loop and bringing the flightpath close to the shore, making it more similar to a holding pattern. The only problem that there seems to be no scheduled flights to Faro from the South, so it would have to be a diverted flight.

  69. That Flightradar24.com site is very eye-opening. Astonishing to realize how much air traffic there is at any one time over the earth – especially between major hubs. Wow!

  70. You are a black-magician, not a scientist or person that is capable of sharing information 🙂 Thanks for letting us know by failing to address our questions. I am not going to repeat myself or respond to you. You can delete my posts if you want. I am here to poison your spell & mantra with light and moving on to serve the RIGHT websites. I work in a higher field than you, so even if I am erased, they can never take the life of a real G. I need light in major way, gonna f*ck my girl, she is gonna get paid in light today! I wish you all the best 🙂

  71. Multiple times I have seen a jet following a dark shadow like line and leaving a trail. The line will then visibly move off to the side and disappear. What is going on in this case? It is not a shadow caused by the trail because it is miles ahead and behind the jet itself.

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